This invention relates to a construction of a connecting portion between a floor frame member and a side frame member in a vehicle such as an automobile.
For example, Japanese Laid-Open Utility Model Publication No. Hei 2-120291 (1990) discloses a frame connecting portion of an automobile in which a front side member is connected to a front end of a front floor stringer (floor frame member) provided on a front floor pan (floor panel). The frame connecting portion is constructed in such a manner that the front floor stringer and the front side member are stacked, one upon another, a lower end of a dash panel is inserted between them, along their stacked surfaces and these three members are fixed to each other.
Hitherto, in such a frame connecting portion, as described above, the frame members have been connected to each other by spot welding or MIG welding.
However, the frame connecting portion connected by spot welding, or MIG welding, has the following problems.
In order to obtain a necessary and sufficient strength against strong and large energy given to the frame connecting portion, a large number of welding points and a long welding line are required so that a space large enough for a welding gun is necessary on both sides of the welded portion. As the result, a large hole must be bored at the floor panel side and is apt to cause depreciation of the floor panel rigidity.
In addition, the spot welding and MIG welding are likely to cause a large decrease in performance according to various conditions.
Further, the performance of the spot welding varies with plate thickness. Thus, there is a limit in a weldable plate thickness.